Diesel and direct injection gasoline engines may have fuel injection systems that directly inject fuel into engine cylinders. The fuel is injected to an engine cylinder at a higher pressure so that fuel can enter the cylinder during the compression stroke against elevated cylinder pressure. The fuel may be elevated to the higher pressure by a mechanically driven fuel pump. Fuel pressure at the outlet of the fuel pump is controlled by adjusting an amount of fuel that flows through the fuel pump.
One way to control flow through the fuel pump is via a solenoid operated metering valve. In one example, the solenoid is operated to close the metering valve during a pumping phase of the fuel pump. Closing the metering valve prevents fuel from flowing into or out of an inlet of the fuel pump. The closing time of the metering valve may be adjusted to control flow through the fuel pump. However, when the solenoid changes state to allow the metering valve to open or close, the solenoid or a portion of metering valve impacts a surface within the metering valve housing. The impact can produce noise, vibration, and harshness (NVH) in the pump as well as the surrounding components. Specifically, the impact may generate a ticking noise. As a result, customer dissatisfaction may be increased. The vibration from the impact may also damage components in the fuel pump, as well as the surrounding components (e.g., engine block, oil pan, cam covers, front cover, and/or intake and exhaust manifolds) through vibrational propagation, thereby decreasing component longevity.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for operating a fuel pump. The method may include decreasing a pump chamber pressure, passively opening a metering valve coupled to a pump chamber in response to the decreasing, and while the metering valve is open, generating a rotational output via a motor, transferring the rotational output into an actuation force applied to the metering valve via a metering valve actuation device, and inhibiting the metering valve from closing via sustaining application of the actuation force.
In this way, the metering valve may be passively opened without any NVH and during certain operating conditions the metering valve actuation device is configured to inhibit the metering valve from closing, enabling the amount of the fuel supplied by the fuel pump to downstream components (e.g., the fuel rail) to be adjusted. As a result, fuel pressure control is improved.
The type of metering valve actuation device used in the pump may be selected to reduce (e.g., substantially inhibit) NVH caused by contact between the metering valve and the metering valve actuation device. In one example, the metering valve actuation device is a screw slider configured to translate a rotational force from the motor into a linear actuating force applied to the metering valve. It will be appreciated that the screw slider velocity may approach zero when contacting the metering valve. Thus, the fuel pump can be operated with little or no impact between the metering valve and the metering valve actuation device. As a result, metering valve opening and closing noises may be reduced when compared to solenoid operated metering valves.
In another example, the metering valve may be a reed valve. When a reed valve is used in the fuel pump the likelihood of vibration caused by read valve impact is reduced. Furthermore, the reed valve may be less costly than other types of valves such as check valves or solenoid valves, thereby reducing the cost of the fuel pump.
The present description provides several advantages such as reducing fuel delivery system noise, increasing the longevity of the fuel pump and surrounding components, and providing improved fuel pressure control.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.